Our objective is to develop a fluorescence polarization (FP)-based technology platform that will enable a wide variety of biological measurements including homogeneous immunoassays, high-throughput screening assays for drug discovery, multiplex detection of biological molecules and identification of microbial and viral pathogens. This will be accomplished by the use of FP techniques that employ semiconductor nanoparticles (quantum dots, QDs) functionalized with biomolecular ligands. The method will enable rapid measurement of analytes in a wide variety of samples while virtually eliminating interfering autofluorescence, resulting in an enhanced signal-to-noise ratio. In addition, the method will enable single-step determination of target analyte, without the need to separate free from bound analyte. QDs offer significant advantages over organic fluorophore dyes, including the ability to use larger-molecular weight biomolecular probes in FP assays. Moreover, the requisite instrumentation is inexpensive and can be easily miniaturized. In this Phase I program we will perform proof-of-concept experiments in order to demonstrate the feasibility of using QD-labeled ligands for the measurement of biological entities using FP.